Control of Competing N−H Insertion and Wolff Rearrangement in Dirhodium(II)-Catalyzed Reactions of 3-Indolyl Diazoketoesters. Synthesis of a Potential Precursor to the Marine 5-(3-Indolyl)oxazole Martefragin A
作者:James R. Davies、Peter D. Kane、Christopher J. Moody、Alexandra M. Z. Slawin
DOI:10.1021/jo050303h
日期:2005.7.1
Dirhodium(II)-catalyzed reaction of 3-indolyl α-diazo-β-ketoester 25 in the presence of hexanamide results in competing metal carbene N−H insertion and Wolff rearrangement. The corresponding phenyl diazoketoester 32, on the other hand, gives only the product of N−H insertion, suggesting that the indole moiety is more prone to 1,2-rearrangement. The competing processes were investigated in a range of
在己酰胺的存在下,吡啶鎓(II)催化的3-吲哚基α-重氮-β-酮酸酯25的反应导致竞争的金属卡宾NH插入和Wolff重排。另一方面,相应的苯基重氮酮酸酯32仅给出NH插入的产物,这表明吲哚部分更倾向于1,2-重排。的竞争过程的范围内的3-吲哚基α重氮基β酮酯(进行了调查36,38,40,44); 这些研究表明,吲哚氮上存在强的吸电子基团可以有效地抑制沃尔夫重排。铱(II)催化剂在促进插入过程方面也比铜或路易斯酸催化剂更有效。N-H插入产物,所述酮酰胺(26,47,49,51,53),进行脱水闭环容易成相应的5-(3-吲哚基)恶唑。NH插入/环脱水方法用于海洋天然产物martefragin A的正式合成中。因此,N -Boc高异亮氨酸酰胺23通过对脱氢氨基酸进行不对称氢化制备,用衍生自N- nosyl吲哚基重氮酯40的铑卡宾进行NH插入,然后进行环化脱水和脱保护,得到5-(3-吲哚基)恶唑玛替fragin